Hand-operated grinding or polishing tool

ABSTRACT

A manual grinding or polishing tool consists of an endless grinding or polishing belt, which is tightened about a substantially flat bar-like profile having at least one limb. The limb or limbs are disposed resiliently in relation to the profile, so that the grinding or polishing belt is held under tension. The resilient material can consist of strip steel or elastomers. Between the grinding or polishing belt and the tool body a resilient intermediate layer can be disposed in the form of an endless belt.

BACKGROUND OF THE INVENTION

The invention relates to a hand-operated abrasive or polishing toolhaving an on-stretched, endless abrasive or polishing belt.

Manual grinding and polishing tools consist of a body on which agenerally foliar abrasive means, i.e., an abrasive cloth or paper, isstretched. They are widely used in the form of files or grinding blocks,the grinding block being able to consist of rubber or cork and otherresilient materials. The abrasive belt holders that are in the form of afile have a flexible, wedge-shaped backing for the belt, and theabrasive or polishing belt is held by a clamp by means of a tighteningscrew. In all these tools it is a disadvantage that only a small portionof the abrasive material can be utilized, because it is not possible toutilize the full stroke of the abrasive file, when, for example, it isnecessary to work in a hard-to-reach location. This leads to a very highconsumption of abrasive material, because only fractions of the fixedlengths, which are necessary in any case, can be used and the rest hasto be discarded unused.

Furthermore, in the known tools the disadvantage exists that, if thebelt material has been overstretched by the work, retightening isnecessary, because otherwise the belt material can catch and tear. Suchretightening is difficult and time-consuming in virtually all suchtools, and in many cases it can be accomplished only to a limitedextent.

Other disadvantages of the known tools lie in their shape, i.e., eitheronly one convex surface or only one planar surface is available for thegrinding or polishing operation.

It has therefore been proposed in U.S. Pat. No. 2,414,036 to provide asan grinding and polishing tool a grinding block with an endless abrasivebelt, this block having acute and obtuse angles around which the endlessbelt is passed, while a resilient pad of felt, rubber or foam rubber canbe disposed between the endless belt and the block. The tightening ofthe abrasive belt around the grinding block can be performed by wedgeelements, since the block itself is divided. It is also possible,however, to dispose intermeshing tooth elements in the interior of thegrinding block, in the form of a rack, and thus to make these toothelements snap into one another by drawing the block apart.

This proposal, which goes back to the year 1945, has been unable tosucceed, because the construction of the grinding block with itstightening means, i.e., the wedges or racks, was not optimallyeffective. As stated above, abrasive media, i.e., grinding belts andsandpapers, elongate on a support and catch, unless they are immediatelytightened. This is not possible in the grinding block of U.S. Pat. No.2,414,036, and instead, if the tension applied by the belt to the blockrelaxes, the tightening means loosens and the belt wrinkles, not only onaccount of its own elongation due to the work it has been doing, butalso because, when the tension relaxes, the tightening means itselffails. In the case of tightening by wedges, the wedges drop out of thegrinding block, and in the case of tightening by racks, the racks snapapart, i.e., the grinding block itself is no longer stable andautomatically falls apart.

The invention is thus addressed to the problem of creating a tool whichpermits complete utilization of the grinding or polishing belt, does notrequire complex tightening of the grinding or polishing belt,automatically keeps the grinding or polishing belt always tight, and hasat least one planar and a plurality of convex working surfaces withvarious radiuses.

This problem is solved by a hand-operated abrasive or polishing toolhaving an endless grinding or polishing belt stretched on it, which hasthe distinctive feature that the tool consists of a substantially flatbar-shaped profile having at least one limb, in which at least one limbis disposed resiliently with respect to the profile or another limb, andthe profile and all limbs are surrounded under tension by an endlessabrasive or polishing belt.

On the basis of the resilient disposition of at least one limb, it ispossible to place the endless abrasive or polishing belt around thehand-operated tool without the need for complex tightening procedures.Furthermore, the endless belt is tightened by the resilient force, suchthat the belt is always sufficiently tight, even when it has elongatedin operation. The belt is held on the tool by its natural friction, butnevertheless it can be shifted with little effort longitudinally, thusassuring a 100% utilization of the belt material if the latter has beenused only at portions of the tool.

The replacement of the abrasive belt is accomplished by the simplesqueezing of one or both limbs. This simplicity of the operation assuresthat the abrasive or polishing belt will not be damaged.

One advantageous development of the invention provides for the profileto be in the form of a rounded handle resiliently adjoining a flat limb.The handle can be made of wood or also of metal or plastic. The limbadjoining it has a flat bar-shaped profile and is resiliently joined tothe handle. The tool therefore has an essentially L-shaped cross sectionin side elevation and, after the abrasive or polishing belt is applied,it forms a triangle with rounded corners and one curved side. Thisconvexly curved side lies in the palm of the hand in use, but it canalso be used in the grinding or polishing of concave surfaces, just asthe top and bottom ends of the curved handle can be used in the case ofthe smaller transitional radiuses. It is especially advantageous that,in this tool, one side of the triangle is formed substantially only bythe stretched abrasive belt or polishing belt. The user thus is able towork curved surfaces quickly and cleanly, because pressing the tool downcauses the belt, which is under spring tension, to assume the shape ofparts of the workpiece without the need to set the tool to a particularradius.

Another very advantageous development of the invention provides for theprofile to be in the form of a shallowly curved bow joining together twolimbs. The radius of this bow is relatively long, i.e., more than 100 mmin any case. It can best be 150 to 250 mm, while on the other hand thelimbs are flat, so that one convex surface and two flat surfaces areavailable for working.

According to one desirable embodiment of the invention the profileterminates at both ends in radiuses, the limbs extending from theseradiuses. By this disposition of radiuses at the transition from theprofile to the limbs, in which these radiuses are relatively small andon the order of between 1 and 6 mm, the abrasive or polishing belt isnot too sharply bent, so that a clean backing of the belt is assuredeven in the case of coarse grits. On the other hand, the result is thatthe belt can be more easily shifted longitudinally. Another advantage ofthis embodiment is that these radiuses make it possible to work increvices in workpieces.

Additional advantageous embodiments of the invention provide for thelength of the profile between the radiuses to be greater than the totallength of the limbs, and for end sections connected by curves to thelimbs to extend toward the bow. Since the sum of the limb lengths issmaller than the length of the profile, it is possible to flex the limbsfar inwardly in order thus to mount the abrasive or polishing belt moreeasily on the tool. Installing the belt is further facilitated by thefact that it is possible to grasp and pull toward one another the endsections joined by radiuses to the limbs and to press them toward oneanother, thereby bringing the limbs close together and thus reducing thecircumference of the abrasive or polishing tool.

The entire tool consists advantageously of a resilient material. Eithernatural or synthetic rubber materials can be used as the resilientmaterial. Very advantageous is the use of elastomers, e.g.,polyurethane, which can equally be molded in the correspondingconfiguration. However, the use of glass fiber-reinforced plastic,especially polyester, has also proven practical. The shape of the toolis to be adapted in each case to the plastic that is used, so that thedesired resilient action is achieved.

An especially preferred embodiment of the invention provides for theresilient material to be a steel strip. This steel strip is generally aspring steel, such as is obtainable commercially, for example, under theVDEH designation CK 53, CK 60, CK 67, MK 75 or MK 101, and in cases inwhich the tool comes in contact with moisture or, in some cases, acidsand alkalies, alloy steels are used, such as those known commercially bythe VDEH designations 67 SICR 5, 50 CRV 4, 58 CRV 4, 12 CrNi 17 7.

For a number of materials it is necessary, especially in polishing, thatthe tool be pressed gently and over a large surface area against theworkpiece. The invention therefore provides for a resilient backing tobe placed between the abrasive or polishing belt and portions of thetool. This backing can best consist of sponge rubber or foam rubber inthe form of an endless belt, but it is also possible to cement thebacking permanently to the profile and/or the limbs, cork having provento be especially suitable in this case.

According to a desirable embodiment of the invention the polishing beltconsists of an endless belt of felt or fabric, i.e., after replacing theabrasive belt with the polishing belt, the initially ground surface canbe treated with polishing pastes.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below with the aid of the drawings,wherein

FIG. 1 is a perspective view of an abrasive tool with an endlessabrasive belt mounted on it,

FIG. 2 shows the same tool in perspective, without an abrasive belt,

FIG. 3 is a cross section of the latter tool,

FIGS. 4 and 5 represent a slightly different geometric configuration,

FIGS. 6 and 7 represent an embodiment of the tool having only one limb.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIGS. 1 to 4, the profile attached to the limbs is formed by a bow 5,which in FIGS. 1 to 3 is in the form of a convex arc 5, and in FIG. 4 ofa concave arc 5. This bow 5 is adjoined by the right radius 2 and theleft radius 3. Both radiuses 2 and 3 merge with the limbs 1, which arejoined by the bends 7 to the end sections 8.

If the thumb and index finger are placed one in each bend 7 and the endsections 8 are squeezed together, the bow 5 is bent and the entirecircumference of the tool is reduced, so that it can be inserted intothe abrasive or polishing belt 6. If pressure on the end sections 8 isthen released, the material springs back and exerts a pressure on theinside surfaces of the abrasive or polishing belt which holds the beltin the given position.

In FIGS. 1 to 4 inclusive, both the bow 5 and the limbs 1 with theradiuses 2 and 3 and the curves 7 consist of a springy steel strip,i.e., the complete holder consists of one and the same material.

The tool shown in FIG. 5, which also consists of one and the samematerial, is similar. In this case, however, it is not a steel but aresilient plastic, preferably Vulcollan. A circumferential rim 12 of thewidth of the abrasive or polishing belt 6 surrounds the basic body 13,which has the eyes 14 which serve for contracting and thus increasingthe curvature of the bow 5.

FIGS. 6 and 7 represent generally L-shaped configurations of theabrasive or polishing tool, in which the bow is formed by the handle 4,which is adjoined by a limb 1. In FIG. 6, this is a limb 1 whichconsists, like the handle 4, of a glass fiber reinforced polyesterresin, whereas in FIG. 7 the limb 1 is a strip of steel which isembedded in a thermoplastic in the handle 4. Also represented in thisfigure is a foam rubber belt 9 which is disposed as a backing betweenthe abrasive or polishing belt and the tool, and has also been made intoan endless belt. This foam rubber belt 9 serves, as explained above, topermit the application of a softer pressure against the workpiece. Asimilar purpose is achieved, as represented in FIG. 4, with the corkbacking 10 applied to the limbs 1.

I claim:
 1. Hand operated abrading or polishing tool comprising anarcuate holder including a substantially flat, bar-like profile portionand two limbs, and an endless abrasive or polishing belt that is undertension encompassing the holder, the substantially flat, bar-likeprofile portion comprising a shallowly curved bow joining together thetwo limbs, which bow is defined at both ends by radii, the limbsextending from these radii in a direction towards each other, and theholder including end sections and bends joining the end sections to thelimbs, the end sections extending in the direction of the bow so as topermit the squeezing together of the limbs to change belts.
 2. Handoperated abrading or polishing tool according to claim 1, in which thelength of the bow defined by the radii is greater than the total lengthof the limbs.
 3. Hand operated abrading or polishing tool according toclaim 1, in which the holder and the limbs comprise the same resilientlyflexible material.
 4. Hand operated abrading or polishing tool accordingto claim 3, in which the resiliently flexible material is a flat steelspring.
 5. Hand operated abrading or polishing tool according to claim3, in which the resiliently flexible material is an elastomer.
 6. Handoperated abrading or polishing tool according to claim 3, in which theresiliently flexible material is a glass fiber-reinforced plastic. 7.Hand operated abrading or polishing tool according to claim 1, in whichbetween the abrasive or polishing belt and the holder there is disposed,at least in partial areas, a resilient intermediate layer.
 8. Handoperated abrading or polishing tool according to claim 7, in which theintermediate layer is a sponge or foam rubber in the form of an endlessbelt.
 9. Hand operated abrading or polishing tool according to claim 7,in which the intermediate layer comprises cork surfaces cementedpermanently to at least a portion of the holder.
 10. Hand operatedabrading or polishing tool according to claim 1, in which the polishingbelt comprises at least one of an endless felt and fabric. 11.Hand-operated abrading or polishing tool comprising a resilientlyflexible holder having a substantially flat, bar-like profile portionand two limbs extending therefrom in a direction towards each other andindividually having end portions, and an endless abrasive or polishingbelt that is under tension encompassing the holder, and each on thelimbs including a curved portion having a finger-hole therein and sodisposed at the end portion of each of the limbs as to permit thesqueezing together of the limbs to change belts.